ABSTRACT
Rudyard Kipling, Hymn of Breaking Strain
This chapter addresses fundamental problems essential to design: determining the location in a part that is likely to fail, and how to analyze stresses and strains that occur at the critical location. The concept of the critical section is discussed, and the terminology of different loads is defined. The concepts of equilibrium and free-body diagrams are then presented, leading to the production of shear and bending moment diagrams for beams. There are numerous methods of producing such diagrams, and three of the most common and powerful techniques are presented. Stress and strain are discussed next, with an emphasis that they are tensors. The common circumstances of plane stress and plane strain are defined. The ability to determine stress states based on orientation is demonstrated through stress transformation equations and Mohr’s circle diagrams, and the procedure for finding principal stresses for a generalized three-dimensional stress state is given. The useful concept of octahedral stresses is presented, and the chapter ends by briefly describing the use of strain gages and rosettes to experimentally determine strains.
